8- and 24-Port Gigabit L2 Managed Power-over-Ethernet (PoE) Switches
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server using EAP encapsulation. Before successfully authenticating, the supplicant can only connect to the authenticator to perform
authentication message exchange or access the network from the uncontrolled port.
Figure 4-136. Authentication.
Figure 4-137 shows a typical configuration using a single supplicant, an authenticator, and an authentication server. B and C is in the
internal network, and D is Authentication server running RADIUS. The switch at the central location acts as an Authenticator
connecting to PC A. A is a PC outside the controlled port, running Supplicant PAE. In this case, PC A wants to access the services on
device B and C. It must exchange the authentication message with the authenticator on the port it is connected to via an EAPOL
packet. The authenticator transfers the supplicant’s credentials to the Authentication server for verification. If authentication is
successful, PC A will be allowed to access B and C via the switch. If there are two switches directly connected together instead of
single one, for the link connecting two switches, it may have perform two port roles at the end of the link: authenticator and
supplicant, because the traffic is bi-directional.
Figure 4-137. Typical configuration.
Figure 4-138 shows the 802.1X authentication procedure. Follow the steps listed below for the login based on 802.1X port access
control management. The protocol used on the right side is EAPOL and the left side is EAP.
1. At the initial stage, the supplicant A is unauthenticated and a port on switch acting as an authenticator is in unauthorized state.
The access is blocked in this stage.
2. Initiating a session. Either the authenticator or the supplicant can initiate the message exchange. If the supplicant initiates the
process, it sends an EAPOL-start packet to the authenticator PAE and authenticator will immediately respond with an EAP-
Request/Identity packet.
3. The authenticator always periodically sends EAP-Request/Identity packets to the supplicant requesting the identity it wants to
authenticate.
LAN
Authenticator
PAE
Services Offered
by Authenticator
(e.g Bridge Relay)
Authenticator’s System
Authentication
Server’s System
Authentication
Server
Supplicant
PAE
Supplicant’
s
System
Uncontrolled port
Controlled port
MAC Enable
Supplicant A
B
C
Authentication Server